If you need to switch DC power, this solid state relay is the perfect mix of quality and affordability. Using the digital outputs from a Phidgets device, you can control the relay to silently switch a DC circuit at 120V/25A or less. There's an indicator LED on the control side of the circuit so you can tell the state of the relay at a glance.

If your SSR is overheating, you should consider getting a heat sink for safety. See below for a list of compatible heatsinks. This SSR comes with a heat transfer pad that can be placed between the metal base of the SSR and the surface it's mounted to in order to help encourage heat flow. It also comes with a diode that can be used to protect your SSR against back EMF.